Method of removing gaseous segregation from metals



METHOD OF REMOVING GASEOUS SEGREGATION FROM METALS No Drawing. Application September 29, 1952, 7

Serial No. 312,170

20 Claims. (Cl. 14813) This invention relates to the removal of gaseous segregation from metal objects and particularly to the removal of hydrogen segregation from ferrous metal objects. The presence of gases in metals is generally known to produce inferior physical properties which in turn result in unacceptable behavior or failure in the finished product fabricated from such metals.

One of the most familiar examples of gaseous segregation in metals is hydrogen segregation in steel and other ferrous metal objects. The presence of hydrogen in steel results in several undesirable physical conditions. One of the most common conditions associated with the presence of hydrogen is the formation of what are commonly termed flakes. These are small internal ruptures within the steel itself. Flakes frequently occur midway between the surface of the steel and the center of a section and are particularly undesirable in the finished product since there is nothing that can be done about them once the object has reached its final finished form. Hydrogen also has a very undesirable embrittling effect upon steel in which it occurs. As in the case of formation of flakes, the nature of this embrittling effect is not completely understood, however, steels in which hydrogen is present in substantial amounts show low ductility and other characteristics of embrittlement. All of these characteristics are generally undesirable in steel products. There has, however, been no way of positively controlling the segregation of hydrogen or other gases in steel and other metals. The only existing commercial practices which seem to reduce the undesirable effects which result from the presence of hydrogen are either to subject the product to special heat treatments or to very slow cooling cycles. Both of these methods are expensive because they tie up equipment and materials for inconveniently long periods of timeoften as long as several days.

I have discovered a method by means of which gaseous segregation in metal objects can be substantially removed and the gases remaining in the metal object distributed substantially homogeneously throughout the object. In a preferred practice of my invention I follow the steps of uniformly heating a portion of a solid metal body from which gaseous segregation is to be removed, advancing the zone of maximum temperature along the body and permitting progressive cooling of the before heated portions during such progression. The progression is carried out at a controlled rate whereat a substantial portion of the gas content migrates with,the advancement of the heated zone. The rate of progression will vary depending upon the conditions, e. g., temperature, composition of the body, etc., however, once conditions are established for a particular body the rate is substantially constant from body to body.

I have found that the method of my invention may be carried out effectively by passing the object through a heated zone into a cooler zone so that the portion of the object in the heated zone is always at a higher temperature than the adjoining portion of the object in the ited States Patent 2,798,018 Fatented July 2, 1957 ice cooler zone and so that the last-heated portion includes an external surface or a portion which is subsequently to be removed from the object, maintaining the lastheated portion at the heating temperature until the balance of the object is substantially lower in temperature and then removing the last-heated portion from the heated zone into the cooler zone.

I have found that the method of my invention is parparticularly satisfactory for the removal of hydrogen from steel and is most effective for this purpose when the heated portions of the steel object are in the austenitic region. I have found that by following this method hydrogen may be moved at least 4 inches in less than 15 minutes by heating and then quenching a steel test piece from one end. For example, a modified Jominy test piece was heated to approximately 1600 F. One end of the heated test piece was then quenched by spraying the end face with cooling liquid. The hydrogen moved through the test piece from the quenched end as the piece cooled and migrated to the portion which was held above 1000 F. for the greatest period of time. The results of this treatment are tabulated in Table I below.

Table 1 Distance Time Above Sample N o Quenched Percent H 1,000 F. in

End Minutes The opposite end of the test piece was permitted to air-cool and a similar migration away from the air-cooled end was noted.

The method of this invention is preferably carried out commercially by progressively removing an object being treated from a furnace in which it has been heated. For example, a billet of steel 10 inches in diameter and 15 feet long can be removed progressively from a furnace maintained in the austenitic temperature range at the rate of about 3 feet per hour and the hydrogen will be evenly distributed at a low concentration in all but the last few feet of the billet which is normally cropped. It is possible to remove the hydrogen from the last few feet if the timing of the withdrawal is correct, that is if the last few feet are retained at the furnace temperature until the hydrogen diffuses into the atmosphere.

The method of this invention may also be carried out by progressively passing an object to be treated through a furnace and into a cooling zone so that the portion leaving the furnace and entering the cooling zone is in contact with a portion within the furnace having a temperature substantially equal to or above that of the portion leaving the furnace.

In any practice of my invention it is of course obvious that the rate of heating and the rate of cooling must be regulated to suit the particular metal object being processed. For example, heating must be regulated to prevent warping or distortion, etc. in the finished piece while at the same time assuring a uniform temperature in the heated portion of the object.

The method of my invention appears to be based upon a flow of gas e. g. hydrogen, from a cooling portion to a portion of higher temperature as if from a place of higher to one of, lower, potential This. results ina metal. object in which a, substantial amount of the. gases. are removed while the remainingv gases. are substantially. homogeneously distributed throughout the ingot from. side to side aswell as from.end,totend.

While I have described the preferredpracticesof my; invention it will be understood 'thatitmaybe otherwise practiced Within the scope of. the following claims.

I claim:

1. Av method of, removing gaseous. segregation from a. solid metal obj ect. haying gaseoussegre gationwhile in said solid state, comprising the steps. of'heating, the object while retainingthe object in the solid state and succes-. sively cooling adjoining portions of, the heated objectso that the last cooled;portion; includes anexternalsurface while maintaining said last-cooledportion at.the heating. temperature until the gases have substantially diffused therefromto the atmosphere.

2. A method of removing gaseous.segregationfroma solid metal object having gaseous segregation while in said solid state, comprising thestepsof passing the object through a heated zone. into acooler, all thewhile. retainq ing the object in the solid state, maintaining the lastheated portion at the heating temperature until the balanceof the object'is substantially lower in temperature anduntil the gases have substantially difr'used from the last-heated portion to the atmosphere and removing the last-hea ted portion from the heated zone to the, cooler zone.

3. A method ofremoving gaseous segregation froma. solid metal object'having gaseous segregation while in said solid state, comprising the steps of passing the object. through a heated zone into a cooler zone so thatthe portion of the object in the heated .zone. istalwaysatahigher temperature than the adjoining portion-of the objectin the cooler zone and so that the last-heated.portion.,in

eludes an external surface, all the while maintaining the object in the solid state, maintaining the last-heated portion at the heating teniperature until the balance of the object is substantially lower in temperature and until the gases have substantially diffused from the last-heated portion to the atmosphere, and then removing the last-heated portion from theheated zone into the cooler zone.

4. A method-of removing gaseous segregation fromasolid metal object having gaseous segregation while in saidsolid, state, comprising the,steps ofi formingtheobject with a 7 portion to be. subsequently removed; passing the object through-a heatedzone into .a cooler zone sof. that theportion to be removedis the last portion to pass. into the cooler zone, all the while retaining the. object. in the solid state, maintainingthe portion to. b erremoved. at theheating temperature until the balance of ;the ob-. ject is substantiallylower intemperature, removingsaid.v

portion fromthe heated zone. andremoying said portion. from the. object.

5. A method of removinghydrogen from .asolid steel:

objecthaving hydrogen segregation. while in. the solidstate, comprising the. steps of heating thesteel object while retaining it in the solid state and successively cooling adjoining portions thereofv so that the last-cooled portion includes an external surface while maintaining the hydrogen has substantially .difiused gtherefrom to the;

an external surface, all the while retaining the objectin the solid state, maintaining the last-heated portion at the heating temperature until the balance of the object is substantially lower in temperature and until the hydrogen has substantially diffused therefrom to the atmosphere, andthen removing the last-heated portion from the heated zone into the cooler zone.

8. The method of removing hydrogen from a solid steel-object, having. hydrogen segregation. while inv the solid state, comprising, thestepsofv forming. the: object.

with aportion.to besubsequently. removed, passing the object through a. heatedzoneinto, acoolerzoneso that theportiomto be. removed-is the lastportion to pass into.

thecoolenzone, allthe whil'eretainingthe object in the solid state, maintaining. the portionto be. removed at the. heatingtemperature. untiLthe. balance. of the object is. substantially lower. in, temperature, removing said. portion frQm. e heatedizone. andremoving said portionfront the. object.

9. Thamethod ofremoving -gaseous segregation from a. solidsteehobject having; gaseous segregationwhile inv said;solid. state,comprising. the.,steps of heating the ob.- ject to -heeaustenitic region,.,all.thewhile. retaining the object, in the. solid state, and successively cooling. ad joiningportionsmf the-,lieated objectso that. the. last: cooled portionincludes an external surface. while maintaining;sa-id lastcooled ;porti.on intheaustenitic. region until'thegases .have substantiallyidiftused therefrom to the, atmosphere.-

10. Themethodof removing. gaseous segregation from a solid steel.objecthaving gaseous, segregation while in said, solid state, comprising the. steps of passing; the object through. a,.hea.ted. zone to raise itSntClTlPEl'fitUIE. to the austenitic region, all the. while. retaining. the. object in thesolid state, passing theobjectinto a cooler zone, maintainingthe last-heated. Portion. in .the austenitic temperature region untilthe balance. of the. object is substantially lower in; temperature and-until the. gases havesubstantially difiused from the last-heated..portion to the atmosphere, and removingthe last-heated portion from. the heated zone tothecoolerzone.

11.. A method of removinggaseous segregation frorna.

solid steel object havinggaseous; segregation whil'ein said solid state, comprising the steps of passing the objectoftheiobject in the .cooler :zoneand so that the last-heated portion. includes anv external@ surface, maintaining the lastheated. portion: in .the. austenitic, temperature. region until the. balance of -,therobject isisubstantiallylower in tem perature. and until the gases haveisubstantiallydiffused fromthe last-heatedg-portion torthe atmosphere, and removing the-last heated portiomfrom the heated zone tothe cooler zone..

12.: A method of removing-a gaseous segregation from a. solid;-steel .object having gaseous-segregation while in said solid state, comprising thesteps offormingthe object with a portion to be subsequently removed,.passing the,

object througha heated zoneto raise-its temperature to the; austeniticyregiom: all; thevwhile retaining the objectin the solid state,- passingthe objectintoa cooler zone in such-manner that the portion-to bet removed is the last PQl'iion to pass intoithecooler zone, maintaining the p or-- solid state, comprising the steps of heating the object to the austenitic region, all the while retaining the object in the solid state, and successively cooling adjoining portions of the heated object so that the last-cooled portion includes an external surface while maintaining said lastcooled portion at the heating temperature until the hydrogen has substantially diffused therefrom to the atmosphere.

14. The method of removing hydrogen from a solid steel object having hydrogen segregation while in the solid state, comprising the steps of passing the object through a heated zone to raise its temperature to the austenitic region, all the while retaining the object in the solid state, passing the object into a cooler zone, maintaining the last-heated portion in the austenitic temperature region until the balance of the object is substantially lower in temperature and until the hydrogen has substantially diffused therefrom to the atmosphere, and removing the last-heated portion from the heated zone to the cooler zone.

15. The method of removing hydrogen from a solid steel object having hydrogen segregation while in the solid state, comprising the steps of passing the object through a heated zone to raise its temperature to the austenitic region, all the while retaining the object in the solid state, passing the object into a cooler zone at a rate such that the portion of the object in the heated zone is always at a higher temperature than the adjoining portion of the object in the cooler zone and so that the last-heated portion includes an external surface, maintaining the lastheated portion in the austenitic temperature region until the balance of the object is substantially lower in temperature and until the hydrogen has substantially diffused therefrom to the atmosphere, and removing the last-heated portion from the heated zone to the cooler zone.

16. The method of removing hydrogen from a solid steel object having hydrogen segregation while in the solid state, comprising the steps of forming the object with a portion to be subsequently removed, passing the object through a heated'zone to raise its temperature to the austenitic region, all the while retaining the object in the solid state, passing the object into a cooler zone in such manner that the portion to be removed is the last portion to pass into the cooler zone, maintaining the portion to be removed in the austenitic temperature region until the balance of the object is substantially lower in temperature, cooling said last-heated portion and removing it from the object.

17. A method of reducing gaseous segregation in solid metal bodies having gaseous segregation while in said solid state, comprising locally heating a portion of the body, advancing the zone of maximum temperature along the body, all the while retaining the object in the solid state, and permitting progressive cooling of the before heated portions during such progression, the progression being at a controlled rate whereat a substantial portion of the gas content migrates with the advancement of the heated zone and maintaining the last-heated zone at the maximum temperature until the gases have substantially diffused to the atmosphere.

18. A method of reducing gaseous segregation in solid metal bodies having gaseous segregation while in said solid state, comprising locally heating a portion of the body while an adjacent portion of the body is at a lesser temperature, advancing the zone of maximum temperature along the body, all the while retaining the object in the solid state, and permitting progressive cooling of the before heated portions during such progression, the progression being at a controlled rate where-at a substantial portion of the gas content migrates with the advancement of the heated zone and maintaining the last heated zone at the maximum temperature until the gases have substantially difiused to the atmosphere.

19. The method of reducing hydrogen content of solid ferrous bodies having hydrogen segregation while in said solid state, comprising locally heating a portion of the body to the austenitic region, advancing the zone of maximum temperature along the body, all the while retaining the object in the solid state, and permitting progressive cooling of the before heated portions during such progression, the progression being at a controlled rate whereat a substantial portion of the gas content migrates with the advancement of the heated zone and maintaining the last heated portion of the body in the austenitic region until the gases have substantially diffused to the atmosphere.

20. A method of reducing hydrogen content of solid ferrous bodies having hydrogen segregation while in said solid state, comprising locally heating a portion of the body to the austenitic region while an adjacent portion of the body is at a lesser temperature, advancing the zone of maximum temperature of the body, all the while retaining the body in the solid state, and permitting progressive cooling of the before heated portions during such progression, the progression being at a controlled rate whereat a substantial portion of the gas content migrates with the advancement of the heated zone and maintaining the last heated portion in the austenitic region until the gases have substantially difiused to the atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Metals Handbook, 1948, p. 1208.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,798,018 July 2, 1957 Gerhard Derge It is hereby certified that error ajapears in the printed specification of the above numbered patent requiring correction and that the said Let uers Patent should read as corrected below.

Column 2, line 39, Table I, fourth column thereof, in the heading,

line 2, for "1,000 F." read 1,000 F. column 3, line 25, after "cooler" and before the comma insert zone column 6, line 51, list of references cited, under the heading UNITED STATES PATENTS" for "Northrop read Northrup Signed and sealed this 29th deg, of October 1957.

(SEAL) Attest:

KARL mm: ROBERT c. WATSON Attesting Officer Commissioner of Patents 

1. A METHOD OF REMOVING GASEOUS SEGREGATION FROM A SOLID METAL OBJECT HAVING GASEOUS SEGREGATION WHILE IN SAID SOLID STATE, COMPRISING THE STEPS OF HEATING THE OBJECT WHILE RETAINING THE OBJECT IN THE SOLID STATE AND SUCCESSIVELY COOLING ADJOINING PORTIONS OF THE HEATED OBJECT SO THAT THE LAST-COOLED PORTION INCLUDES AN EXTERNAL SURFACE WHILE MAINTAINING SAID LAST-COOLED PORTION AT THE HEATING TEMPERATURE UNTIL THE GASES HAVE SUBSTANTIALLY DIFFUSED THEREFROM TO THE ATMOSPHERE 